Longpath DOAS tomography on a motorway exhaust gas plume: numerical studies and application to data from the BAB II campaign T. Laepple, V. Knab, K.-U. Mettendorf, and I. Pundt Institut für Umweltphysik, Ruprecht-Karls-Universität Heidelberg, Heidelberg, Germany
Abstract. This paper presents a procedure for performing and optimizing inversions for
DOAS tomography and its application to measurement data. DOAS tomography is
a new technique to determine 2- and 3-dimensional concentration fields of
air pollutants or other trace gases by combining differential optical
absorption spectroscopy (DOAS) with tomographic inversion techniques. Due to
the limited amount of measured data, the resulting concentration fields are
sensitive to the inversion process. Therefore detailed error estimations are
needed to determine the quality of the reconstruction. In this paper we
compare different row acting methods for the inversion, present a procedure
for optimizing the parameters of the reconstruction process and propose a
way to estimate the error-fields by numerical studies. The procedure was
applied to data from the motorway emission campaign BAB II. Two dimensional
NO2 cross sections at right angles to the motorway could be
reconstructed qualitatively well at different meteorological situations.
Additionally we present error fields for the reconstructions which show the
problems and skills of the used measurement setup. Numerical studies on an
improved setup for future motorway campaigns show, that DOAS tomography is
able to produce high quality concentration maps.
Citation: Laepple, T., Knab, V., Mettendorf, K.-U., and Pundt, I.: Longpath DOAS tomography on a motorway exhaust gas plume: numerical studies and application to data from the BAB II campaign, Atmos. Chem. Phys., 4, 1323-1342, doi:10.5194/acp-4-1323-2004, 2004.